Dravet syndrome is an infant-onset epileptic encephalopathy caused by haploinsufficiency for SCN1A. Seizure onset usually occurs between 6 and 18 months of age with generalized tonic–clonic or hemiclonic seizures, often precipitated by fever. The gene discussed is SCN1A; the disease is encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.